Japanese researchers Susumu Tachi, Masahiko Inami & Yuji Uema from the Graduate School of Media Design at Keio University have come up with an innovative camera/projection system that uses half-mirrors and retroreflectors to provide a really remarkable simulation of a glass car.

The system uses, as you'd probably guess, a series of cameras positioned outside the car to capture the scenery the car is moving through. Conventional projection systems wouldn't be bright enough in the daytime and would distort images too dramatically to be of use. So here's how they solved this tricky problem:

Any conventional projection system would fail for obvious reasons. The projected image wouldn't be bright enough to match the scenery outdoors, at least in the daytime. Images projected on a complex shape would be distorted and would have to be corrected accordingly. A special stereoscopic visor would be needed to view outdoor scenery in three dimensions, and only the driver could enjoy the display in its proper perspective.

We have solved all these problems with a new projector system that reflects light precisely back along the path it has just taken. By doing this, we can project the correct image, in its proper apparent position, directly at the observer—provided that the projector is close enough to the observer's eyes. In order to do this, we can place it on the person's head or mount the projector on the ceiling and have it track the person's movements.

Our retroreflective projection technology, or RPT, uses a screen coated in 50-micrometer glass beads, which produces a very bright reflection. What's more, the system uses one projector for each eye, so it can create a stereoscopic effect with a single screen. No shutter glasses or any other movie-house 3-D equipment are required.

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That's pretty clever, and the results are impressive. Think how effective such a system would be if actually built into a car, using factory-spec retroreflective seat and door panels instead of wrinkly covers.

Think about how useful this would be covering the walls inside an unmarked white van, for all you cops on stakeouts and creepy, creepy stalkers.